Structure Analysis And Optimization Of Wind Turbine Tower

Along with the rapid growth of energy demand in the 21 st century,energy supply has become the indispensable important component in the economy in many countries.Wind energy is widely concerned because of its cleanliness and infinity.With the increasing of size,power and distribution range,wind turbines face severe challenges of economy and security.Tower instability has become the major threat to the safe and stable operation of modern wind power system.T his study is supported by the project Research on Rigid-Flexible Coupling Dynamics of Wind Turbine Blade in Wind Conditions of Hexi Corridor from National Natural Science Foundation of China(No.51565028).The static,dynamic characteristics and stability of a 2MW tower are analyzed in this work.Then,two stages structural optimizations of the tower are performed based on experiments and approximation models to improve the economy and safety.The specific tasks and conclusions are as follows:(1)Static strength and stiffness check of the tower.Three extreme loads(DLC1.3,DLC3.2 and DLC6.1)of the tower are calculated.Then the finite element model of the tower is established to check its static strength and stiffness under different load conditions.The results show that the static strength of the tower meets the design requirements,but the stiffness is overlarge under DLC6.1,which accounts for 0.82% of tower total height and reaches the maximum(0.8%).It indicates that there are safety risks in wind turbines.(2)Analysis of tower natural vibration characteristics and stability.The results indicate that the mass of top components(rotor and nacelle)has significant influence on tower's natural frequency,but eccentricity of top component and the door hole are opposite.The natural frequency of whole model is 0.383 which avoids the 1P and 3P operating frequencies of the wind turbine rotor,and proves the resonating between tower and rotor will not occur.The door hole reduces the critical buckling load of tower from 5.21E7 N to 5.17E7 N.The buckling safety factor of the tower is 0.077,which is smaller than 1 and indicates the tower is stable.(3)An approximate model of tower optimization problem is eatablished.Based on the above analyses,optimal latin hypercube sampling is used to illustrate the relationships between tower responses(displacement,von-Mises stress,mass,natural frequency and buckling critical load)and structure parameters(height,thicknesses and radius).Then,the numerical formulas of tower response with structure parameters are fitted by using response surfaces approach.(4)Structural optimizations of tower and door hole.In the first stage,NSGA-?is employed to optimize the tower structure.A set of pareto solutions are obtained,by comparing the four optimization schemes,the optimal solution for desired design is given.In the second stage,the response surface with max von-Mises stress and door parameters are established base on the above new tower.Then,the Simulated Annealing(SA)is used to optimization door.Finally,the most desired tower is obtained.